If you pay for views rather than duration you incentivise short videos, if you pay for duration you incentivise long videos.
If you go for duration the risk is that you have lots of long easily made videos getting money instead of short hard to make videos. Is that going to harm more things than paying for views?
I think I'd rather have a 10 minute lets-play earn 10x more than one minute physics video than have a playlist of the ten funniest 6s cat videos earn 10x more than one view of minute physics.